There are pros & cons for each.
Cost fact benefits just using 7250 as internet access.
since 7250 will require either $24.99 [10MB] or $44.99 [unlimited] + $15 Broadband Access. If you get VZAccess PcCARD unlimited is [$59.99] plus you still need to get some sort of data plan for 7250 to get emails so additional $24.99.

Cons would that you cannot surf the internet and talk on the phone at the same time since you would be using 7250 as the modem.
Also you would need to use lame wired [USB] cable to connect to the PC.

I haven't done thruput comparison but I assume that its about the same.
Depending on the location and with latest 7250 FW & BB Desktop you can
1x and EVDO speed when its available.

I would still stick with have to use 7250 use a modem since most places I go I can use my t-mobile acct to login wireless on my laptop.